Re: [PATCH] ipv6: Enable RFS sk_rxhash tracking for ipv6 sockets

On Wed, Apr 06, 2011 at 08:07:33PM +0200, Eric Dumazet wrote:

Le mercredi 06 avril 2011 à 13:54 -0400, Neil Horman a écrit :

quoted

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index d7037c0..aa3e327 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c

@@ -505,6 +505,8 @@ int udpv6_queue_rcv_skb(struct sock * sk, struct sk_buff *skb)
 	int rc;
 	int is_udplite = IS_UDPLITE(sk);
 
+	sock_rps_save_rxhash(sk, skb->rxhash);
+
 	if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
 		goto drop;
 

Problem is every packet received might have a different rxhash if
multiple senders are active. 

This can hurt performance (cache misses on RFS table) on a DNS server
workload for example.

This is why we used on ipv4 :

if (inet_sk(sk)->inet_daddr)
	sock_rps_save_rxhash(sk, skb->rxhash);

Ok, I can absolutely do that, I'll respin shortly.  Just to make sure I
understand how to do this, the ipv6 equivalant of inet_daddr is
inet6_sk(sk)->daddr, correct? I ask because the above v4 equivalent is stored in
the sk_common struct, and I want to make sure I'm testing the right data. 

Also, do we have a macro already to see if an ipv6 address is all zeros?  I'm
not finding one, but I'd hate to re-invent the wheel if I'm just missing it.

Only arm RFS on UDP if socket is bound to a given remote peer.

BTW you forgot Tom Herbert. (I added him in CC)

Thanks, sorry Tom, Just took the output of get_maintainers.pl without checking
all the results.
Neil